This invention relates to apparatus for initiating sonobuoy functions and, more particularly, to shape-memory alloy activators, configured and connected to initiate sonobuoy float inflation and hydrophone cable payout and release.
Passive sonobuoys are developed having a hydrophone multiple water depth selection mechanism initiated after deployment in the water. Active sonobuoys are designed for hydrophone depth selection change by radio command when the sonobuoy is in the water. Both sonobuoys respond to depth selection by releasing a preset amount of suspension cable. The mechanical release is typically actuated by an explosive cartridge actuated device (CAD) which while providing the required mechanical force also has the adverse side effect of ensonifying the surrounding water. Additionally, a CAD is used to fire a pointed projectile into the sealed end of a high pressured gas bottle for inflating an expandable flotation device. Here again the CAD device generates a high intensity sound that is directly coupled to the water and can be heard for long distances. Since a requisite feature of today's sonobuoys is covertness, a high intensity sound tends to compromise that feature.